[Potential impact of water transfer project from Yangtze River to Huaihe River on snail spread and schistosomiasis transmission].

ABSTRACT

OBJECTIVE: To investigate the possibility of spread of snails and transmission of schistosomiasis japonica due to the construction of water transfer project from Yangtze River to Huaihe River. METHODS: In order to understand the current endemic situation of schistosomiasis in the project area, the distribution of snails was surveyed by routine methods, level of anti-schistosome antibody in human sera was detected by indirect haemagglutination test (IHA), and the prevalence of schistosomiasis in cattle was detected by egg hatching method. The snail survival and reproduction were observed in Chaohu Lake area(experimental area) and a control area for one year. RESULTS: Snail density was high in two starting points, from where the water in Yangtze River will be directed to Huaihe River. In counties of Wuwei and Hexian, through which the project will be built, the positive rate of anti-schistosome antibody in residents was 22.11% (168/760) and 18.59% (37/199), schistosomiasis prevalence in cattle was 2.42% (9/371) and 0.2% (2/997), respectively. Schistosomiasis was also endemic in Juchao District of Chaohu City. Snails respectively from grassland and hilly area were collected and put in Chaohu Lake for breed and newborn snails were found one year later. During the egg-laying season, the survival rate of snails from grassland in 2 experiment areas and a control area was 11.3%-16.7%, 3.0%-20.8% and 4.7%-14.7% respectively (chi2 = 0.093, 0.760, P > 0.05; chi2 = 0.647, 0, P > 0.05), and that of snails from hilly area was 24.1%-44.4%, 37.8%-67.3% and 86.3%-93.1% respectively (chi2 = 9.575, 5.302, P < 0.05; chi2 = 56.863, 36.218, P < 0.05). There was no significant difference between the experimental area and the control area on the number of eggs in the ovaries of the same type female snails. CONCLUSION: The one-year observation reveals that the construction of the project might result in spread of snails and transmission of schistosomiasis japonica in the relevant areas.